Ar-Ar ages and ore-forming material sources of the Na Bop-Pu Sap Pb-Zn Deposit in the Cho Don Area, Northeastern Vietnam

Purpose. This study aims to investigate the ore mineralization characteristics and genesis models and assess the mineral potential of the Na Bop-Pu Sap lead-zinc deposit, which represents a novel deposit type in northeastern Vietnam. Methods. This research employs several analytical methods, including microscopic analysis of ore minerals, sulfur and lead isotope analysis of ore sulfide minerals, Ar-Ar dating of sericite samples contemporaneous with sulfide ores, and fluid inclusion studies to determine ore-forming temperatures. Findings. Field observations suggest that the ore deposits manifest as Pb-Zn-bearing veins along faults and as strata-bound ore types within early Devonian sedimentary carbonate rocks. Microscopic analysis identifies galena, sphalerite, pyrrhotite, pyrite, and arsenopyrite as ore minerals, accompanied by gangue minerals such as quartz, calcite, and dolomite. Sulfur-isotope values (δ34S) of galena, sphalerite, and pyrite range from +0.10 to +8.49‰ (mean = +4.48‰), suggesting a magmatic origin with a deep source. Lead isotope ratios of galena (206Pb/204Pb: 18.451-18.651, 207Pb/204Pb: 15.685-15.836, 208Pb/204Pb: 38.909-39.501) point to an upper crustal source. Ar-Ar dating of sericite yields plateau ages of 237.1 ± 2.3 Ma and 242.6 ± 2.4 Ma, correlating with the timing of lead-zinc mineralization, as indicated by the syntectonic texture between sericite minerals and sulfide ores. Fluid inclusion studies on calcite from galena-hosted veins suggest moderate temperatures (201-245°C) and salinities (4.65-8.00 wt.% NaCl equiv.), indicative of evolving 2O – NaCl systems and variable physicochemical conditions. These findings classify the Na Bop-Pu Sap deposit as an epithermal-type deposit. Originality. The Na Bop-Pu Sap Pb-Zn deposit in northern Bac Kan Province, Vietnam, is one of the largest deposits in the Cho Don area. It is notable for its significant reserves and unique metal combination. Despite extensive knowledge of Pb-Zn mineralization, the timing and origin of ore-forming fluids remain poorly understood. Practical implications. This study provides insights into the genesis and spatio-temporal evolution of Pb-Zn mineralization in the Na Bop-Pu Sap deposit within the Cho Don area.